System for manufacturing a rotor having an MMC ring component and a unitary airfoil component

ABSTRACT

A system for manufacturing an integrally bladed rotor is provided. This system includes a ring component, wherein the ring component further includes at least one metal matrix composite and a continuous radially outwardly facing blade conical surface; an airfoil component, wherein the at least one airfoil component has been created from a single, unitary piece of material and further includes a plurality of individual airfoil blades and a continuous radially inwardly facing blade conical surface; and inertia welding means for frictionally engaging under an axially applied weld load the ring component and the airfoil component to effect an inertia weld therebetween along the conical surfaces.

BACKGROUND OF THE INVENTION

The described invention relates in general to integrally bladed rotorsfor use in gas turbine engines, and more specifically to a method forpreparing a BLING rotor that incorporates at least one metal matrixcomposite into the ring component of the rotor or the airfoil componentof the rotor.

Rotors, such as those used with gas turbine engines typically include abasic rotor body and a plurality of rotor blades attached thereto. Rotorblades may be anchored in specific recesses formed in the rotor body orthe rotor blades may be formed integrally with the rotor body itself.Integrally bladed rotors are referred to as BLISKS (bladed disc) if adisc-shaped basic rotor body is utilized or a BLING (bladed ring) if aring-shaped basic rotor body is utilized. BLING rotors offer distinctadvantages over BLISK rotors because the BLING design results in alarger internal cavity than is typically possible with the BLISK design.This cavity provides space within the engine that may be used foradditional equipment such as, for example, an embedded electricgenerator and/or heat exchanger. The BLING design may also provideimproved rotor dynamic damping and higher E/rho (by as much as 70%),compared to conventional metal disks, and even to integrally bladedBLISK rotors. The BLING design also enables the use of metal matrixcomposite (MMC) for the basic rotor body. In the context of gas turbineengines, high strength, low density MMC may offer significant advantagesover monolithic metal alloys, including a significant decrease in theweight of engine components.

Known methods for manufacturing MMC reinforced BLING rotors typicallyutilize hot isostatic pressing (HIP), which includes diffusion bondingof various components. The HIP process consolidates metal matrixcomposites into higher density, uniform, fine grain structures. However,incorporating an MMC ring into a multi-load path structure, i.e., rotorto blade, is technically challenging and requires a large number ofprocess controls to ensure that no internal defects are present afterthe structure has been created. A thermal expansion coefficient mismatchbetween the MMC ring and monolithic material used for the blades mayproduce a residual compressive stress field along the bonding surface.Resultant internal defects are not detectable using non-destructiveinspection techniques; thus, strict process controls must beimplemented. Consequently, the expense involved in creating a BLINGrotor of suitable quality using MMC and HIP diffusion bonding may beconsiderable compared to the cost of a BLISK rotor machined from aconventional forging.

Thus, there is a need for a reliable, economically-sound method formanufacturing BLING rotors that incorporate MMC, wherein the completedrotor may be treated to relieve residual compressive stress, and whereinbond surface integrity can be inspected using conventional,non-destructive methods for detecting internal defects.

SUMMARY OF THE INVENTION

The following provides a summary of exemplary embodiments. This summaryis not an extensive overview and is not intended to identify key orcritical aspects or elements of the present invention or to delineateits scope.

In accordance with one exemplary embodiment, a system for manufacturingan integrally bladed rotor is provided. This system includes at leastone ring component, wherein the at least one ring component furtherincludes: at least one metal matrix composite; and a continuous radiallyoutwardly facing blade conical surface; at least one airfoil component,wherein the at least one airfoil component has been created from asingle piece of material and further includes: a plurality of individualairfoil blades; and a continuous radially inwardly facing blade conicalsurfaces; and inertia welding means for frictionally engaging under anaxially applied weld load the at least one ring component and the atleast one airfoil component to effect an inertia weld therebetween alongthe conical surfaces.

In accordance with another exemplary embodiment, an integrally bladedrotor is provided. This rotor includes at least one ring component,wherein the at least one ring component further includes: at least onemetal matrix composite and a continuous radially outwardly facingconical surface; at least one airfoil component, wherein the at leastone airfoil component has been created from a single piece of materialand further includes: a plurality of individual airfoil blades; and acontinuous radially inwardly facing conical surface; and wherein the atleast one ring component and the at least one airfoil component havebeen frictionally engaged with one another along the conical surfaces byinertia welding means.

In yet another exemplary embodiment, a method for manufacturing anintegrally bladed rotor is provided. This method includes providing atleast one ring component, wherein the ring component further includes:at least one metal matrix composite; and a continuous radially outwardlyfacing conical surface; at least one airfoil component, wherein the atleast one airfoil component has been created from a single piece ofmaterial and further includes: a plurality of individual airfoil bladesformed from the single piece of material; and a continuous radiallyinwardly facing conical surface; and using inertia welding means forfrictionally engaging under an axially applied weld load the at leastone ring component and the at least one airfoil component to effect aninertia weld therebetween along the conical surfaces. This method alsoincludes the step of subjecting the assembled integrally bladed rotor toheat treatment sufficient to relieve internal stresses generated byinertia welding.

The use of BLING rotors in gas turbine engines can offer significantadvantages over other designs. For example, combining airfoil componentsand rotor rings into a single structure improves strength to weightratios and gas turbine engine performance, in general. Additionalfeatures and aspects of the present invention will become apparent tothose of ordinary skill in the art upon reading and understanding thefollowing detailed description of the exemplary embodiments. As will beappreciated, further embodiments of the invention are possible withoutdeparting from the scope and spirit of the invention. Accordingly, thedrawings and associated descriptions are to be regarded as illustrativeand not restrictive in nature.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated into and form a partof the specification, schematically illustrate one or more exemplaryembodiments of the invention and, together with the general descriptiongiven above and detailed description given below, serve to explain theprinciples of the invention, and wherein:

FIGS. 1-2 are a front view of the airfoil component of the presentinvention showing both the general shape of the airfoil blades prior tothe blades being machined from a single piece of material and thegeneral shape of the angular, i.e., conical, prep-weld surface.

FIG. 3 is a cross-section of an exemplary airfoil component and bladeand a cross-section of the MMC reinforced rotor ring of the presentinvention prior to inertia welding of the airfoil component and the ringcomponent.

FIG. 4 is a cross-section of an exemplary airfoil blade and across-section of the MMC reinforced rotor ring of the present inventionfollowing inertia welding of the airfoil component and the ringcomponent.

DETAILED DESCRIPTION OF THE INVENTION

Exemplary embodiments of the present invention are now described withreference to the Figures. Reference numerals are used throughout thedetailed description to refer to the various elements and structures. Inother instances, well-known structures and devices are shown in blockdiagram form for purposes of simplifying the description. Although thefollowing detailed description contains many specifics for the purposesof illustration, a person of ordinary skill in the art will appreciatethat many variations and alterations to the following details are withinthe scope of the invention. Accordingly, the following embodiments ofthe invention are set forth without any loss of generality to, andwithout imposing limitations upon, the claimed invention.

The disclosed system includes at least one ring component, wherein theat least one ring component further includes: at least one metal matrixcomposite; and a continuous radially outwardly facing conical surface;at least one airfoil component, wherein the at least one airfoilcomponent has been created from a single, unitary piece of material,e.g. metal, and further includes: a plurality of individual airfoilblades formed from the unitary piece of material and a continuousradially inwardly facing conical surface; and inertia welding means forfrictionally engaging under an axially applied weld load the at leastone ring component and the at least one airfoil component to effect aninertia weld therebetween along the conical surfaces.

Metal matrix composite (MMC) is a composite material that includes atleast two constituents, one of which is a metal. The other constituentmay be a different metal or another material, such as a ceramic,organic, or other nonmetallic compound. When at least three materialsare present, the composite is referred to as a hybrid composite. Eachpart of the material is either the matrix or a reinforcement. The matrixis essentially the “frame” into which the reinforcement is embedded andmay include metals such as aluminum, magnesium, titanium, nickel,cobalt, and iron for providing a compliant support for thereinforcement. The reinforcement material is embedded into the matrix.The reinforcement does not always serve a purely structural purpose(reinforcing the compound), but is also used to affect compositeproperties such as wear resistance, friction coefficient, materialdamping, or thermal conductivity. The reinforcement can be eithercontinuous, or discontinuous. Continuous reinforcement uses monofilamentwires or fibers such as carbon fiber or silicon carbide. Embeddingfibers into the matrix in a certain direction creates an isotropicstructure in which the alignment of the material affects its strength.Discontinuous reinforcement uses “whiskers”, short fibers, or particles.The most common reinforcing materials in this category are alumina andsilicon carbide.

Compared to monolithic metals, MMCs have: higher strength-to-densityratios, higher stiffness-to-density ratios, better fatigue resistance,better elevated temperature properties (Higher strength, lower creeprate), lower coefficients of thermal expansion, better wear resistanceand dynamic damping. MMC reinforcements can be divided into five majorcategories: continuous fibers, discontinuous fibers, whiskers,particulates, and wires. With the exception of wires, which are metals,reinforcements generally include ceramics or nonmetallic compounds.Continuous fibers may include boron, graphite (carbon), alumina, andsilicon carbide. A number of metal wires including tungsten, beryllium,titanium, and molybdenum have been used to reinforce metal matrices.Numerous metals have been used as matrices, including: aluminum,titanium, magnesium, nickel, cobalt, iron, and copper alloys andsuperalloys. The superior mechanical properties of MMCs drive their use.An interesting characteristic of MMCs, however, and one they share withother composites, is that by appropriate selection of matrix materials,reinforcements, and layer orientations, it is possible to tailor theproperties of a component to meet the needs of a specific design. Forexample, within broad limits, it is possible to specify strength andstiffness in one direction, coefficient of expansion in another, and soforth. This is often not possible with monolithic materials. Monolithicmetals tend to be isotropic, that is, to have the same properties in alldirections.

Inertia welding is a welding process in which energy utilized to weldmaterials to one another is supplied primarily by stored rotationalkinetic energy of the machine used for welding. As part of the processof inertia welding, one of two work pieces is typically connected to aflywheel and the other work piece is restrained from rotating. Theflywheel is accelerated to a predetermined rotational speed, therebystoring a certain amount of energy. The drive motor is disengaged andthe work pieces are forced together by the friction welding force. Thiscauses the facing surfaces to rub together under pressure. The energystored in the rotating flywheel is dissipated as heat through frictionat the weld interface, thus welding the two surfaces together as theflywheel speed decreases ending with the weld stopping the flywheel.Because there is no melting of metal, solidification defects such as gasporosity, segregation or slag inclusions, do not typically occur. Jointpreparation is not usually critical, and machined, saw cut, and evensheared surfaces are most often weldable. Resulting joints are of forgedquality, with a complete butt joint weld through the contact area. Noconsumables, e.g., flux, filler, and shielding gases, are used and noweld splatter typically occurs. Sparks are minimal, as well.

With reference to FIGS. 1-4, an exemplary embodiment of this inventionprovides a system and method for manufacturing a BLING rotor thatincludes an airfoil component 11 and a ring component 20. The airfoilcomponent includes a plurality of individual airfoil blades 12, whichhave been formed (e.g. machined) from a single piece of material such asa cast or forged 360° ring to create a bladed rotor platform. As shownin FIGS. 1-2, the bottom portion of the 360° ring includes an angularwelding region (i.e., a weld-prep surface) that forms an angular surface14, which is referred to herein as a “conical surface”, although othergeometries are possible. Surface 14 may be convex, concave, or straight.As shown in FIGS. 2-3, ring component 20 includes a MMC reinforced core22, which provides a zone in the rotor which is reinforced by layers orbundles of fibers that are typically oriented circumferentially in thedirection of rotor rotation. Ring component 20 also includes acontinuous angular or “conical” surface 24 that corresponds to theairfoil surface 14. Surface 24 may also be concave, convex, or straight.

Manufacturing fiber-reinforced (i.e., MMC) ring component 20, typicallyincludes the step of forming a ring-like structure, wherein at least onefiber within the ring extends circumferentially in the direction ofrotor rotation. The circumferentially oriented fiber may be a singlecontinuous filament or material strand, a stack of multiple fiber layersoriented in a radial manner within the ring, or one or more untwistedbundles of continuous filaments or strands, i.e., a tow or tows. Thefiber may be made from SCS6 or other ceramic or non-metallic materialshaving a carbon coating around the fiber outer surface to preventreaction (e.g. oxidation of fiber core) between fiber and metal matrixduring the HIP process. The fiber layer may also be made with at leastone discontinuous or bundle of nano size whisker fiber arranged inrandom or circumferential directions or in layers. The coated fiber maybe mixed with wet metal alloy slurry, e.g., Ti-alloy, Ni-alloy, Al-alloyor other powder metals with adhesive binder, by plasma spray, or byplasma vapor deposition method to hold fiber in place forming a metalmatrix composite lamina. After the coated metal matrix composite laminais stabilized in a layered shape, wind coated fibers are layered arounda mandrel to form a ring shape structure. The metal matrix compositelaminar ring is consolidated by HIP and/or by a sintering process in acarbon, TZM, or steel-tooling fixture. A region of additional materialis typically included along the outer diameter of the fiber-reinforcedring. This “build-up region” is usually at least 0.5 inches (1.27 cm) inheight and may be created by plasma spray of powdered metal, or bystacking metal foils to the thickness required. The build-up region isthen consolidated by HIP and/or by a sintering process in a carbon, TZM,or steel-tooling fixture.

In the exemplary embodiment, airfoil component 11 is welded to thefiber-reinforced ring component 20 using inertia or friction weldingmethodology. As previously described, airfoil component 11 includes abladed rotor platform having a continuous inwardly facing conicalsurface 14 oriented in a radial manner about the central axis of therotor. Airfoil component 11 is mounted into one end of suitable inertiawelding equipment. Ring component 20, which includes a continuousoutwardly facing conical surface 24, is mounted into the other end ofthe inertia welding equipment. Ring component 20 is then rotated to apredetermined contact speed and brought into contact with the airfoilcomponent 10, thereby forming a weld between the components usingparameters typical for inertia welding. The inwardly facing conicalsurfaces are thus frictionally engaged with the outwardly facing conicalsurfaces under an axially applied weld load and a friction weld occursbetween the two components at the angled surfaces. Heat generated by theinertia welding process does not typically affect MMC fiber or thegeneral shape and/or geometry of the airfoils and the weld surfaces.Typically, the angle of each conical surface relative to the componenton which it is formed is about 15°-75° relative to the centerline ofrotation. Other angles are possible for affecting the engagement ofBLING rotor components.

Once the weld is complete, the extra stock material around airfoil root16 is removed by machining or other means to below the weld line, as isextra material 17 at the periphery of ring component 20 that has beenforced out from under the component interface during the inertialwelding process. Thus, any un-welded areas in the radial space betweenthe airfoil sections are removed, as are any defects that may begenerated in these areas during the welding process. As shown in FIG. 8,this re-machined surface becomes inner flow path 28, thereby placingweld line 26 through each airfoil slightly above the inner flow path.

Following the inertia welding of the rotor components, the assembledBLING rotor is typically subjected to heat treatment sufficient torelieve internal stresses generated by the welding process and torestore materials properties that are important to the properfunctioning of the gas turbine engine. As will be appreciated by theskilled artisan, the specific type of post-weld heat treatment will varybased on the materials, i.e., the alloys, used in creating the rotor.The inclusion of MMC in the airfoil component and/or ring componentprevents or reduces inspection problems associated with excessive heatand or melting; thus, bond surface integrity may be inspected usingconventional Eddy current, ultrasonic, or other non-destructiveinspection (NDI) methods for detecting internal defects.

While the present invention has been illustrated by the description ofexemplary embodiments thereof, and while the embodiments have beendescribed in certain detail, it is not the intention of the Applicant torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to any of the specific details, representativedevices and methods, and/or illustrative examples shown and described.Accordingly, departures may be made from such details without departingfrom the spirit or scope of the applicant's general inventive concept.

1. A method for manufacturing an integrally bladed rotor, comprising:(a) providing a ring component, wherein the ring component furtherincludes: at least one metal matrix composite; and continuous, radiallyoutwardly facing conical surface; (b) providing an airfoil component,wherein the airfoil component has been created from a single piece ofmaterial and further includes: a plurality of individual airfoil bladesformed from the single piece of material; and a continuous, radiallyinwardly facing conical surface; (c) using inertia welding means forfrictionally engaging under an axially applied weld load the ringcomponent and the airfoil component to effect an inertia weldtherebetween along the conical surfaces; and (d) removing a quantity ofmaterial around the base of each airfoil blade following the welding ofthe airfoil component to the ring component to a diameter smaller thanthe weld diameter between each conical surface.
 2. The method of claim1, further comprising subjecting the assembled integrally bladed rotorto heat treatment sufficient to relieve internal stresses generated byinertia welding.
 3. The method of claim 1, wherein the ring component ofthe integrally bladed rotor extends circumferentially and axiallyrelative to the rotor's center of rotation, wherein at least onereinforcing fiber is included within the ring, and wherein thereinforcing fiber extends circumferentially in the direction of rotorrotation.
 4. The method of claim 3, wherein the circumferentiallyoriented fiber further comprises at least one of a single, continuous,fiber tow and a group of randomly arranged nano-size whisker fibers. 5.The method of claim 3, wherein the circumferentially oriented fiberincludes a stack of multiple fiber layers oriented in a radial mannerwithin the ring.
 6. The method of claim 5, wherein the fiber layersinclude nano-size whisker fibers arranged randomly, circumferentially,or in layers.
 7. The method of claim 5, wherein the angle of eachconical surface is about 15°-75° relative to the rotor's centerline ofrotation.